Broadly speaking, extrusion processes are known. Typically, thermoplastic polymer (“TP”) material is fed into an extruder in a powdered, granular or pelletized form and then converted into a continuous stream of melted TP material by a heated barrel screw. In such applications, a certain amount of slippage or bypass of the melted TP material generally occurs along the screw flights and between the screw and the barrel. This slippage and bypass, although useful for efficient TP processing, also causes unwanted problems—the old color or feed stock will tend to contaminate a new color or new feed stock, necessitating production of undesired or unusable material until the original color or TP is cleared completely from the unit. Also, portions of the feed material can adsorb onto internal metal surfaces and can build up and cause problems over time.
One remedy is to clean the extruder with a purge compound. See for example, U.S. published patent application 2003/0221707 A1 to Blanton et al. A common type of purge compound comprises a thermoplastic material having a higher melting point than the material being purged from the extruder. Such purge compounds can also carry abrasives or chemical cleaners to aid in cleaning the equipment as the purge compound is moved through the extruder. Conventional purge materials can be expensive, inefficient, environmentally unfriendly, overly abrasive and/or otherwise problematic. A need therefore persists for improved purge compositions and methods for cleaning plastics processing equipment, e.g., are relatively inexpensive and efficient, do not necessitate disassembly of equipment to accomplish proper cleaning and do not cause undue abrasion or other damage when used.